US20060208751A1

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Publication number: US20060208751A1
Application number: US11/328,315
Authority: US
Inventors: Chih-Chung Chen
Original assignee: MJC Probe Inc
Current assignee: MPI Corp
Priority date: 2005-03-15
Filing date: 2006-01-10
Publication date: 2006-09-21
Also published as: US7446548B2; TW200632324A; TWI261672B

Abstract

An elastic micro probe includes an electrically conductive and stretchable spring, which has a first end, a second end opposite to the first end, and connection points disposed adjacent to the first end for connection to an external element, an electrically conductive probe body, which has a first end connected to the second end of the spring and a second end vertically upwardly protruding over the first end of the spring, and an electrically conductive tip, which has a bottom side connected to the second end of the probe body such that when the tip is pressed, the probe body is forced to move the second end of the spring, thereby causing the spring to be stretched and elastically deformed.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to micro probes and more particularly, to an elastic micro probe for use as a circuit connection interface. The invention relates also to the fabrication of the elastic micro probe.

2. Description of the Related Art

When testing high-density or high-speed electrical devices (for example, LSI or VLSI circuits), a probe card having a big amount of elastic micro contacts (probes) shall be used. By means of the resilient and electrically conductive material property of the elastic micro probes, the probe card is used as an electric connection medium between the test apparatus and the device to be tested, for example, an LSI chip, VLSI chip, semiconductor wafer, semiconductor chip, semiconductor package, or printed circuit board. Elastic micro contacts can also be used as lead wire means for an IC package. For easy understanding of the present invention, elastic micro contacts are described as probes for probe cards.

Conventionally, elastic micro probes, more particularly upright probes are made by means of forging technology or micro electromechanical technology.

FIG. 1 shows anelastic probe5 according to the prior art. This structure ofelastic probe5 is comprised of a plurality of parts that are separately made through a precision manufacturing process and then assembled together. Through a precision manufacturing process, the parts can be made subject to the desired precision. However, it is complicated to assemble the precision parts. Because the spring member for this elastic probe is a thin and elongated metal wire member, it has a low stability. When compressed, the spring member may be biased to rub against the peripheral wall, resulting in unnecessary wearing and tip contact instability.

In order to eliminate the problem of complicated assembly process, there are manufacturers who employ a semiconductor integration manufacturing process to fabricate spring probes directly from a substrate. This semiconductor integration manufacturing process eliminates the assembly process.FIG. 2ashows aspring probe1 made according to this semiconductor integration manufacturing process. According to this design, thespring body3 of thespring probe1 blocks the solder joint2 (seeFIG. 2a). When damaged, thespring probe1 is not replaceable. By means of thespring body3 between thetop tip4 and thebottom solder joint2, thespring probe1 is compressively deformable upon a pressure. The H (height) to W (width) ratio of a spring probe is normally below 3.7.FIG. 2bshows a spring probe of H/W<3.7 compressed by a downward force F.FIG. 2cshows a spring probe of H/W>3.7 compressed by a downward force F. As shown inFIG. 2c,the spring probe buckles when being compressed. In order to prevent excessive deformation, the H (height) W (width) ratio of a spring probe must be limited to a certain level. When reducing the width of the spring probe, the height of the spring probe must be relatively reduced. In this case, the amount of elastic deformation the spring probe itself can provide is relatively reduced, i.e., the power of the spring probe to compensate flatness error relative to the surface condition of test sample and the limitation of mechanical leveling control is relatively reduced. Following the development of miniaturized semiconductor and package technology, this design of spring probe cannot meet actual requirements. Further, the alignment error of the multilayer structure between thesolder joint2 and thetip4 cannot assure accurate positioning of the tip during bonding. Further, because the spring probe is completely exposed to the outside, it tends to be damaged.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide an elastic micro probe manufacturing process, which is free from the limitation of the H (height) W (width) ratio of the spring, practical for the fabrication of miniaturized elastic micro probes.

It is another object of the present invention to provide an elastic micro probe manufacturing process, which employs micro electromechanical technology to reduce labor-intensive assembly procedure, thereby saving much manufacturing time and improving product precision.

It is still another object of the present invention to provide an elastic micro probe manufacturing process, which is practical for the fabrication of elastic micro probes that have the solder joint disposed at the top side so as to facilitate the maintenance and replacement of probes.

It is still another object of the present invention to provide an elastic micro probe manufacturing process, which is practical for the fabrication of micro spring contacts that have the solder joint and the tip set close to each other for positive positioning to achieve a high precision.

It is still another object of the present invention to provide an elastic micro probe manufacturing process, which employs an embedded architecture, preventing damage of the spring by an external force.

According to the present invention, the elastic micro probe comprises an electrically conductive and stretchable spring, which has a first end, a second end opposite to the first end, and at least one connection point disposed adjacent to the first end for connection to an external circuit; an electrically conductive probe body, which has a first end connected to the second end of the spring and a second end vertically upwardly protruding over the first end of the spring; and an electrically conductive tip, which has a bottom side connected to the second end of the probe body such that when the tip is pressed, the probe body is forced to move the second end of the spring, thereby causing the spring to be stretched and elastically deformed.

The present invention also discloses a method of making the elastic micro probe mentioned above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of an elastic micro probe according to the prior art.

FIG. 2ais a side view of a spring probe according to another prior art.

FIG. 2bis a schematic drawing showing a spring probe compressed according to the prior art.

FIG. 2cis a schematic drawing showing a spring probe compressed and buckling according to the prior art.

FIG. 3 is a side view of an elastic micro probe according to the present invention.

FIG. 4 is a schematic drawing showing insertion of the elastic micro probe ofFIG. 3 into a well at a substrate.

FIG. 5 corresponds toFIG. 4, showing the elastic micro probe bonded to the substrate inside the well.

FIG. 6 corresponds toFIG. 5, showing the tip of the elastic micro probe pressed against a test sample.

FIG. 7 is a cutaway view showing another installation example of the elastic micro probe shown inFIG. 3.

FIGS. 8a-8hshow an elastic micro probe manufacturing steps according to a second embodiment of the present invention.

FIGS. 9a-9lshow an elastic micro probe manufacturing steps according to a third embodiment of the present invention.

FIGS. 10a-10jshow an elastic micro probe manufacturing steps according to a fourth embodiment of the present invention.

FIG. 11a-11cshow elastic micro probe manufacturing steps according to a fifth embodiment of the present invention.

FIG. 12 illustrates the structure of an elastic micro probe according to a sixth embodiment of the present invention.

FIG. 13 shows an alternate form of the spring for elastic micro probe according to the present invention.

FIG. 14 shows another alternate form of the spring for elastic micro probe according to the present invention.

FIG. 15 shows still another alternate form of the spring for elastic micro probe according to the present invention.

FIG. 16 shows an elastic micro probe made according to the seventh embodiment of the present invention.

FIG. 17 shows the elastic micro probe ofFIG. 16 installed in a substrate.

FIG. 18 corresponds toFIG. 17, showing the tip forced downwards and the spring members stretched.

FIG. 19 is a schematic drawing showing the status of an elastic micro probe upon a pressure according to an eighth embodiment of the present invention.

FIG. 20 is a schematic drawing showing an elastic micro probe installed in a socket and a shielding layer added to the outside of the socket according to the present invention.

FIG. 21 is a schematic drawing showing an elastic micro probe embedded in a substrate, a grounding line arranged at an outer side relative to the signal line in the substrate according to the present invention.

FIG. 22 is a schematic drawing showing multiple elastic micro probes assembled in a multilayer form according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring toFIG. 3, an elasticmicro probe100 in accordance with the first embodiment of the present invention is shown comprising aspring10, aprobe body14, and atip15.

Thespring10 is an electrically conductive, single-screw, compressible, stretchable, hollow member made through micro electromechanical technology, having afirst end11, asecond end12 opposite to thefirst end11, and twoconnection points13 disposed adjacent to thefirst end11 at two sides.

Theprobe body14 is an electrically conductive, rod-like member set inside thespring10, having one end, namely, the bottom end connected to thesecond end12 of thespring10 and the other end, namely, the top end vertically upwardly protruding over thefirst end11 of thespring10.

Thetip15 is an electrically conductive, conical member or pyramid, having the bottom side thereof connected to the free end (top end) of theprobe body14.

FIGS. 4-6 show the assembly process of the elasticmicro probe100 and its use to probe atest sample18. At first, thespring10 is inserted into a well161 at asubstrate16 that has a depth greater than the length (height) of thespring10 after fully extension, and then the connection points13 of thespring10 are respectively connected to a respective top solder joint162 at the substrate16 (seeFIG. 4), for enabling the electric signal detected by thetip15 to be transmitted through acircuit163 that is disposed in thesubstrate16 and electrically connected to the solder joints162 to an external test apparatus through anelectrical pad17. When connecting the elasticmicro probe100 to the test sample18 (seeFIG. 6), the top end of thetip15 is kept in contact with thetest sample18. In order to ensure positive contact between thetip15 and thetest sample18, thesubstrate16 is set closer to thetest sample18. When moving thesubstrate16 toward thetest sample18, a pressure is given from thetest sample18 to thetip15, thereby causing theprobe body14 to move thesecond end12 of thespring10 in the same direction, and the distance between thesecond end12 of thespring10 and thetest sample18 is relatively increased (seeFIG. 6). This design ensures positive contact between thetip15 and thetest sample18. Further, by means of the stretching action of thespring10, the elasticmicro probe100 is free from the limitation of H (height) to W (width) ratio as encountered in the aforesaid prior art design. In a spring probe made according to the prior art design, the connection point (solder joint) is disposed at the bottom side and the contact point (the point to contact the test sample) is disposed at the top side. If the structure of the elastic micro probe is excessively thin and long, i.e., if the H (height) to W (width) ratio of the elastic micro probe is excessively high, the micro spring contact will buckle when compressed, resulting in instability (please refer to description of the prior art andFIG. 2c). The stretchable design of thespring10 has the connection points13 provided at the top side so that thespring10 is kept straight and will not be curved when stretched. Because thespring10 is free from the limitation of H (height) to W (width) ratio, the invention meets miniaturized specification requirements, and thespring10 can be made having a sufficient length to provide the desired amount of elastic deformation.

Further, because the elastic micro probe according to the present invention is made in integrity through micro electromechanical technology, the invention eliminates the labor-intensive probe-by-probe assembly procedure or high-cost automated assembly procedure, thereby accelerating probe card manufacturing speed and greatly improving the precision of the product. Further, because the connection points of the elastic micro probe according to the present invention are disposed at the top side, the solder joint and the tip are kept close to each other, assuring conformity of the solder joint positioning precision and the tip positioning precision. Further, the elastic micro probe adopts an embedded architecture, i.e., the elastic micro probe is embedded in a well at a substrate, the substrate can be made in the form of a raisedsocket19 as shown inFIG. 7 or a hollow frame (not shown). Further, the embedded architecture of the present invention has the elastic micro probe be well protected against external objects.. If the elastic micro probe is damaged and a replacement is needed, the top-sided solder joint (connection points) can easily be melted for replacing probes. Therefore, the maintenance work of the probe card is easy.

FIGS. 8a-8hshow an elastic micro probe manufacturing method according to the second embodiment of the present invention. According to this manufacturing method, a socket and an elastic micro probe are made in integrity, thereby simplifying the manufacturing process. This manufacturing method includes the steps of:

(a) preparing asubstrate70 having acircuit71 as shown inFIG. 8a;

(b) laying ashielding layer72 having a patterned opening on thecircuit71 of thesubstrate70 as shown inFIG. 8b,whichshielding layer72 can be photoresist and which patterned opening can be achieved by means of a semiconductor photo lithographic technology;

(c) depositing aconductive layer73 on the top side of thesubstrate70 and theshielding layer72 by evaporation deposition, sputtering deposition, or electroplating as shown inFIG. 8c;

(d) forming asacrificial layer74 on the top side of theconductive layer73 and leveling thesacrificial layer74 by grinding as shown inFIG. 9d,whichsacrificial layer74 can be formed of one or multiple metal materials, polymers, or metal oxide materials by means of micro electroforming, spray-painting, or chemical vapor deposition technology;

(e) removing theshielding layer72, and depositing astructural metal layer75 on the same place of the position of theshielding layer72, then leveling thesacrificial layer74 and thestructural metal layer75 by grinding as shown inFIG. 8e,whichstructural metal layer75 can be formed of one or multiple highly conductive metal materials by means of micro electroforming, evaporation deposition or sputtering deposition technology;

(f) repeating steps (b)-(e) to form the desired spring, probe body, and socket structure in which aconnection metal75′ is provided as shown inFIG. 8fby laminating thestructural metal layer75 one above another; wherein theconnection metal75′ can be formed of solder materials such as tin, tin lead alloy, gold, silver, bismuth for easy melting during a replacement work;

(g) bonding the spring, probe body and socket structure thus obtained with atip76 which is made through a precision mechanical processing procedure and temporarily secured to another substrate as shown inFIG. 8g;and

(h) removing thesacrificial layer74, the conductinglayer73 and the adhesive means that secures thetip76 to the other substrate so as to obtain the desired socket-based elastic micro probe as shown inFIG. 8h.

FIGS. 9a-9lshow an elastic micro probe manufacturing method according to the third embodiment of the present invention. This embodiment is substantially similar to the aforesaid second embodiment of the present invention with the exception of the fabrication of thetip76. According to this embodiment, the procedure of making thetip76 comprises the steps of:

(a) preparing a monocrystalline silicon substrate80 (or a substrate having an electrically insulative surface) as shown inFIG. 9a;

(b) laying afirst shielding layer81 on the top surface of thesubstrate80 by LPCVD (low pressure chemical vapor deposition) as shown inFIG. 9b,whichfirst shielding layer81 can be formed of silicon nitride, silicon oxide, silicon dioxide, polymers, or a photoresist;

(c) laying asecond shielding layer82 having an opening on the top surface of thefirst shielding layer81 as shown inFIG. 9c;

(d) removing the exposed part of thefirst shielding layer81 away from the opening of thesecond shielding layer82 by RIE (reactive ion etching) as shown inFIG. 9d;

(e) removing thesecond shielding layer82, and then etching thesubstrate80 with an anisotropic etching liquid (for example, potassium hydroxide), so as to form anotch83 corresponding to the opening of thesecond shielding layer81 as shown inFIG. 9e;

(f) removing thefirst shielding layer81 as shown inFIG. 9f;

(g) depositing aconductive layer84 on the top surface of thesubstrate80 as shown inFIG. 9g,which conductivelayer84 can be formed of titanium, titanium-based metal material, or any of a variety of metal materials that have a high conductivity and adhesion power;

(h) laying ashielding layer85 on the top surface of theconductive layer83, which shielding layer has an opening disposed right above thenotch83 as shown inFIG. 9h;

(i) depositing anenhanced film86 on the surface of theconductive layer84 above thenotch83 subject to the use of amask86′ as shown inFIG. 9i;

(j) electroforming astructural metal layer87 above thenotch83 and then leveling thestructural metal layer87 by grinding as shown inFIG. 9j;

(k) plating abonding layer89 on the top surface of thestructural metal layer87 subject to the use of amask88 as shown inFIG. 9k;and

(l) removing theshielding layer85 so as to obtain a tip at the substrate as shown inFIG. 9l.

FIGS. 10a-10jshow an elastic micro probe manufacturing method according to the fourth embodiment of the present invention. The above-mentioned embodiment is to make an elastic micro probe directly on a substrate by lamination. Alternatively, the socket and the probe body can be produced at the same time and then fastened to the substrate. The manufacturing method according to this embodiment comprises the steps of:

(A) preparing asubstrate90 having aconical notch91 at the top side thereof (the conical notch of the substrate can be made by a precision machine processing process, chemical etching, or hot press molding) and then depositing aconductive material92 on the top surface of thesubstrate90 as shown inFIG. 10a(the conductive material can be deposited on the substrate by evaporation deposition, sputtering deposition, or electroplating);

(B) depositing anenhanced film93 on the surface of thenotch91 subject to the use of a mask (similar toFIG. 9k) by means of sputtering deposition or evaporation deposition as shown inFIG. 10b;

(C) laying apatterned shielding layer94 over thenotch91 as shown inFIG. 10c;

(D) depositing asacrificial layer95 on the top surface of thesubstrate90 by electroplating, sputtering deposition, or evaporation deposition as shown inFIG. 10d;

(E) removing theshielding layer94 as shown inFIG. 10e;

(F) electroforming astructural metal layer96 on the top side of thenotch91 and then leveling thesacrificial layer95 and thestructural metal layer96 by grinding as shown inFIG. 9f;

(G) repeating steps (C) to (F) to laminate the desired structure (for example,connection metal96′), and then depositing abonding layer97 subject to the use of a mask as shown inFIG. 10g,whichbonding layer97 can be formed of solder metal such as gold, tin, tin lead alloy, tin silver alloy, tin bismuth alloy, or the like by means of electroplating, sputtering deposition or evaporation deposition, and the mask used can be a flat plate having a patterned through hole;

(H) bonding thebonding layer97 to anelectronic substrate98 as shown inFIG. 10h;

(I) removing thesacrificial layer95 as shown inFIG. 9i;and

(J) etching theconductive material92 so as to strip off thesubstrate90 as shown in FIG10j.

Further, theconnection metal96′ shown inFIGS. 10g-10jcan be a solder material such as tin, tin lead alloy, gold, silver, or bismuth for easy melting during a replacement work.

FIGS. 11a-11cshow an elastic micro probe manufacturing method according to the fifth embodiment of the present invention. This embodiment is to have the elastic micro probe be directly embedded into the substrate or socket. The manufacturing method according to this embodiment comprises the steps of (a) preparing an elastic micro probe, which comprises asubstrate21, aspring23, atip22, aprobe body2, a connectingblock27 connected between thespring23 and thesubstrate21, and a seed layer (or sacrificial layer)28 connected between the connectingblock27 and the spring23 (seeFIG. 11a), (b) bonding a substrate25 (or socket) to thespring23 to have thespring23 be inserted into a well26 at the substrate25 (seeFIG. 11b), and (c) removing theseed layer28 so as to strip off the connectingblock27 and the substrate21 (seeFIG. 11c). Thus, the elastic micro probe and the electronic substrate are bonded together.

Further, tenon and mortise joint means may be provided between the elastic micro probe and the electronic substrate (or socket) to reinforce the positioning.

In the aforesaid various embodiments of the present invention, the spring of the elastic micro probe is a singe-screw spring. Alternatively, the spring can be made having a rectangular or triangular cross section, or any of a variety of other geometric profiles.

FIG. 12 shows an elastic micro probe constructed according to the sixth embodiment of the present invention. According to this embodiment, thespring31 does not have a helical structure. Bending a metal spring strip into or directly shaping a detoured structure that is stretchable makes thespring31.

In order to prevent biasing of the tip of the elastic micro probe upon contact with the test sample, the spring of the elastic micro probe can be made in any of a variety of other symmetric forms. For example, thespring32 shown inFIG. 13 has double-helix structure; thespring32′ shown inFIG. 14 has a triple-helix structure; thespring32″ shown inFIG. 15 has two detoured structures. These

springs

32,32′,32″ distribute the pressure evenly in different directions when stretched, preventing biasing of the tip.

FIG. 16 shows an elastic micro probe made according to the seventh embodiment of the present invention. According to this embodiment, the elastic micro probe comprises aprobe body41, atip42, fourspring members43, and twobonding pads44. Theprobe body41 has one end terminating in a connectingportion411. Thetip42 is connected to the other end of theprobe body41. Thebonding pads44 are symmetrically disposed at two sides relative to theprobe body41 and equally spaced from the connectingportion411 at a distance. Thespring members43 are arched alike members arranged in pairs and curved in two reversed directions, each having a first end connected to the connectingportion411 and a second end connected to onebonding pad44.

The aforesaid elastic micro probe can be made by lamination by means of micro electromechanical technology.

FIGS. 17 and 18 show an elastic micro probe bonded to asubstrate45 according to the present invention. During installation, theprobe body41 and thespring members43 are inserted into a well451 at thesubstrate45, and then thebonding pads44 are respectively bonded to a solder joint452 at thesubstrate45 outside thewell451. Thesubstrate45 has acircuit453 laid therein to connect the solder joints452.

When thetip42 received a pressure during probing, theprobe body41 is forced to stretch the spring members43 (seeFIG. 18). Therefore, this embodiment achieves the objects of the present invention.

FIG. 19 shows an elastic micro probe made according to the eighth embodiment of the present invention. This embodiment allows thetip51 to bias laterally subject to a different test sample. At illustrated, theprobe body52 is disposed at an outer side relative to thespring53 and opposite to theconnection point531 of thespring53. When thetip51 received a pressure during probing, theprobe body52 and the connectingpoint531 that are respectively connected to the two distal ends of thespring53 are forced to stretch thespring53, allowing thetip51 to bias laterally so as to scrub away the metal-oxide over the test sample and make better conductivity.

In order to prevent signal coupling among densely installed elastic micro probes, a shielding layer56 (of dielectric material) is added to the outside of thesocket55 to provide an optimum signal shielding effect and also to increase the transmission bandwidth. If the elastic micro probe is embedded in asubstrate57 as shown inFIG. 21, a grounding line59 (grounding conductive material) may be arranged at an outer side relative to thesignal line58 in the substrate to increase the transmission bandwidth and to improve signal quality.

FIG. 22 is a schematic drawing showing multiple elasticmicro probes100 assembled in a multilayer form. According to this arrangement, each elastic micro probe at the lower side has a relatively longer probe body so that the pitch among the tips of the elasticmicro probes100 can be reduced effectivelly.

Claims

1. An elastic micro probe comprising:

a spring, which is electrically conductive and stretchable, having a first end, a second end opposite to said first end, and at least one connection point disposed adjacent to said first end for connection to an external element;

a probe body, which is electrically conductive, having a first end connected to the second end of said spring and a second end vertically upwardly protruding over the first end of said spring;

when said second end of flexible part is pressed, said probe body is forced to move the second end of said spring, thereby causing said spring to be stretched and elastically deformed.

2. The elastic micro probe as claimed inclaim 1, wherein the second end of said probe body further mounts a tip member.

3. The elastic micro probe as claimed inclaim 1, wherein the second end of said probe body is shaped into a tip.

4. The elastic micro probe as claimed inclaim 1, wherein said spring is comprised of at least one single-screw spring member.

5. The elastic micro probe as claimed inclaim 1, wherein said spring and said probe body and said tip are made in integrity by means of micro electromechanical technology.

6. The elastic micro probe as claimed inclaim 1, wherein said spring is comprised of at least one spring strip.

7. The elastic micro probe as claimed inclaim 1, wherein said spring surrounds said probe body.

8. The elastic micro probe as claimed inclaim 1, wherein said probe body is disposed outside said spring.

9. The elastic micro probe as claimed inclaim 1, comprising plural said connection points disposed symmetrically nearby the first end of said probe body; wherein said probe body has a connecting portion at the first end thereof; said spring comprises a plurality of spring strips arranged in pairs and curved in two reversed directions, each spring strip having a first end connected to one of said plural connection points and a second end connected to the connecting portion of said probe body.

10. The elastic micro probe as claimed inclaim 1, which is mounted to a substrate and sink into a well in a the substrate.

11. A micro probe assembly comprising a plurality of elastic micro probes ofclaim 10, wherein said substrates are alternatively arranged at different elevations for keeping the tips of the elastic micro probes more compact.

12. The elastic micro probe as claimed inclaim 10, wherein the well of said substrate holding the elastic micro probe is peripherally mounted with a dielectric material and a metal conductive grounding material.

13. The elastic micro probe as claimed inclaim 1, which is mounted inside a well in a socket.

14. The elastic micro probe as claimed inclaim 13, wherein the well of said socket holding the elastic micro probe is peripherally mounted with a dielectric material and a metal conductive grounding material.